Fungicide

ABSTRACT

A new valuable fungicide based on N-tridecyl-2,6-dimethylmorpholine as the active ingredient, the said ingredient being in the form of microcapsules of which the wall consists of a polymer while the core contains the active ingredient.

The present invention relates to a fungicide based onN-tridecyl-2,6-dimethylmorpholine, in which the active ingredient is inthe form of microcapsules.

The use of N-tridecyl-2,6-dimethylmorpholine (tridemorph) as a fungicidehas been disclosed in German Patent No. 1,164,152.

The high vapor pressure of the active ingredient causes losses of thelatter when used in climatic regions having fairly high averagetemperatures, since a part of the active ingredient vaporizes before itcan exert its fungicidal action. Hence, a second application of activeingredient is in most cases necessary after some time.

It is an object of the present invention to avoid these disadvantages.

We have found that a fungicide based onN-tridecyl-2,6-dimethylmorpholine as the active ingredient does notsuffer from these disadvantages if the active ingredient is in the formof microcapsules which contain the active ingredient in their corewhilst their walls consist of a crosslinked or non-cross-linkedsynthetic or natural polymer or a mixture of such polymers, the wallformation being effected by coacervation or by some other type ofdeposition of wall material or by a wall-forming reaction at theinterface between the capsule core and the surrounding medium.

Each microcapsule is a separate reservoir of active ingredient. Thecapsule walls reduce the rate of vaporization of the active ingredient.This results in a depot action, because a given amount of activeingredient exhibits a fungicidal action for a longer period afterapplication to the plant, and also results in controlled liberation ofthe active ingredient over a substantial period of time, since thevaporization of the active ingredient can be delayed to a greater orlesser extent depending on the nature of the microcapsules.

When using the non-encapsulated active ingredient at substantialconcentrations, phytotoxic phenomena are sometimes observed with certainplants. These are not observed when using the fungicide according to theinvention, which substantially broadens the scope of the activeingredient.

The rate of vaporization of the active ingredient from the microcapsulecan be regulated by varying the nature of the wall material, the wallthickness, the active ingredient/wall material ratio and the degree ofcrosslinking of the microcapsule wall.

The nature of the wall material essentially depends on the encapsulationprocess. The following may be mentioned as examples:

Encapsulation by the coacervation process, for example as described inU.S. Pat. No. 2,800,457. The wall materials used are crosslinked naturalpolymers, e.g. gelatin or gum arabic.

Encapsulation by the interfacial condensation process (U.S. Pat. No.3,577,515, German Published Application DAS No. 1,519,925, GermanLaid-Open Application DOS No. 1,444,415 and U.S. Pat. No. 3,429,827).The wall materials used in this process are nylons obtained bypolycondensing terephthalic acid dichloride with a diamine/triaminemixture.

Encapsulation by the phase separation process as described in GermanLaid-Open Applications DOS Nos. 2,119,933 and 2,237,503. This process ispreferred. It employs a crosslinked acrylate-based copolymer as the wallmaterial.

The microcapsules obtained on encapsulation have diameters ranging from0.01 to 5,000 μm. Microcapsules with diameters of from 0.1 to 50 μm arepreferred. The capsules may be in the form of individual capsules orcapsule agglomerates.

Instead of just the active ingredient, the capsules may also containmixtures with other active ingredients or with compounds which aremiscible with the active ingredient and inert toward the core materialand the wall material. These include, for example, high-boiling solvents(100°-250° C.), such as various types of plasticizer, e.g. diethylhexylphthalate and diisobutyl phthalate, various polyethylene waxes, montanwaxes. They modify the viscosity of the active ingredient in thecapsules. Mixtures of these active ingredients with a high-boilingliquid which is inert toward the wall material and toward the activeingredient are preferred. The microcapsule core can consist of anymixture of tridemorph and inert component, but a proportion of from 0 to50% by weight of the latter, based on the mixture, is preferred.

Various weight ratios of core material to wall material may be employed.The state of aggregation and nature of the core material and thediameter of the microcapsules may be a factor in this decision. In thepreferred phase separation process, the ratio is in general from 1:1 to30:1, preferably from 3:1 to 15:1. For a constant capsule diameter, thewall thickness is determined by the ratio of core material to wallmaterial. The wall material may be crosslinked after carrying out theencapsulation. By this means, the degree of impermeability of themicrocapsules, and the retarded vaporization of the active ingredient,can be controlled.

The aqueous dispersion of the capsules obtained from the microcapsulemanufacturing process can be concentrated, for example by removing theexcess water by distillation or centrifuging.

Where necessary, further additives may be incorporated into themicrocapsule dispersion, e.g. thickeners, wetting agents anddispersants, binders, fillers or anti-foam agents. For greater ease ofstorage it is possible to produce a dry microcapsule powder from themicrocapsule dispersion. Various processes may be used for isolating themicrocapsules from the dispersion and drying them, e.g. freeze-drying ordrying on trays after isolating the microcapsules by sieving orcentrifuging. A particularly suitable process is spray-drying. For thispurpose, the capsule dispersion is sprayed in a spray-dryer, using aone-fluid or two-fluid nozzle or a whirler disc. If the drying gases areused at an input temperature of, for example, from 100° to 140° C. andan output temperature of, for example, from 50° to 70° C., afree-flowing dry powder is obtained. The individual capsules in thepowder have the same diameters as in the dispersion. The size of thepowder particles depends on the size of the spray droplets and thesolids content of the dispersion. The powder is readily redispersible inwater. Using this method, a dispersion of the microcapsules isreconstituted.

The Examples which follow illustrate the manufacture of the microcapsuledispersions and their advantageous application.

EXAMPLE 1

Using the preferred phase separation process, the wall materials and themicrocapsule dispersion are essentially manufactured as described inGerman Laid-Open Application DOS No. 2,119,933 and German PublishedApplication DAS No. 2,213,755.

71 parts by weight of tridemorph are dissolved in 6 parts by weight ofisopropanol and 65 parts by weight of chloroform. This solution isthoroughly dispersed, at room temperature, in a solution of 50 parts byweight of a 10% strength aqueous polyvinylpyrrolidone solution (K valueof the polyvinylpyrrolidone=90, measured on a 1% strength solution inwater) and 200 parts by weight of water, the dispersing device usedbeing an Ultra-Turrax from Jahnke and Kunkel. A solution of 60 parts byweight of a 40% strength wall material solution inchloroform/isopropanol, as described in Example 1 of German Laid-OpenApplication DOS No. 2,119,933, and 65 parts of chloroform is then addedslowly at from 30° to 60° C., under constant thorough dispersion. Thedispersion time is selected to give particles having a diameter of from5 to 10 μm. The emulsion is diluted with 250 parts by weight of water ina distillation flask, whilst stirring, and the auxiliary solvents, i.e.the chloroform and isopropanol, are distilled off completely. Thecapsule wall is then hardened, in the course of 2 hours at 80° C., byadding 6 parts by weight of 40% strength formaldehyde solution.

A microcapsule dispersion which has a solids content of 18.5% by weightand a tridemorph content of 12.5% by weight is formed. The viscosity ina DIN cup (FB 4 mm), measured as the flow time, is 14.4 seconds. Themicrocapsules are spherical and have a mean diameter of from 6 to 10 μm.The cured wall material forms a capsule round the tridemorph.

The encapsulation is virtually complete; the proportion of freetridemorph outside the microcapsules is less then 0.03% by weight. Therate of vaporization of the active ingredient from the microcapsules islower by a factor of 90 than that of the non-mixed, non-encapsulatedactive ingredient.

In order to ensure that the aqueous capsule dispersion is stable onstorage, from 1 to 2% by weight of a 25% strength dispersion of apartially crosslinked copolymer containing carboxylic acid, as describedin German Laid-Open Application DOS No. 2,217,690, can be added to thedispersion. The viscosity, measured with a Brookfield viscometer,spindle 4, at 100 rpm, is from 400 to 600 centipoise, whilst measured asthe flow time from a DIN cup (FB 4 mm) it is from 40 to 50 sec.

To produce a dry powder, the aqueous micro-capsule dispersion is sprayedwith air into a spray-dryer, using a two-fluid nozzle. Using a dryinggas input temperature of 120° C., the amount of dispersion introducedinto the spray-dryer is adjusted to give an output temperature of 60° C.

The dry powder thus obtained is readily redispersible.

The dry microcapsules have the same appearance as the capsules dispersedin water.

EXAMPLE 2

The procedure described in Example 1 is followed, but thetridemorph/isopropanol/chloroform solution to be encapsulated is addedto the solution of wall material in chloroform. This tridemorph/wallmaterial/chloroform/isopropanal solution is then dispersed in theaqueous polyvinylpyrrolidone solution, after which the encapsulation iscompleted, using the method already described, by removing theisopropanol and chloroform and then carrying out a treatment withformaldehyde. The microcapsules have a diameter of from 5 to 15 μm.

EXAMPLE 3

The procedure described in Example 1 is followed, but when distillingthe isopropanol and chloroform, the material is not diluted with waterin the distillation flask. Furthermore, the wall material used is amaterial prepared, as described in German Laid-Open Application DOS No.2,119,933, by copolymerizing 20% by weight of propanediol monoacrylateacetylacetate, 50% by weight of methyl methacrylate and 30% by weight ofacrylic acid. Under these conditions, the distillation of the auxiliarysolvent takes place completely, without interfering with themicrocapsules.

A microcapsule dispersion having a solids content of 34.8% by weight isobtained, while the proportion of free tridemorph outside themicrocapsules is 0.015% by weight.

The microcapsule dispersion prepared as described in Examples 1 to 3were tested for their biological activity, in comparison withnon-encapsulated tridemorph.

EXAMPLE 4

Wheat mildew

Leaves of pot-grown wheat seedlings of the "Jubilar" variety are sprayedwith aqueous microcapsule dispersions and after the spray coating hasdried, the plants are dusted with oidiae (spores) of wheat mildew(Erysiphe graminis var. tritici). The test plants are then set up in agreenhouse at from 20° to 22° C. and from 75 to 80% relative atmospherichumidity. After 10 days, the degree of development of the mildew fungi,and the leaf damage, are determined. An aqueous tridemorph emulsionwhich contains 80% of active ingredient and 20% of emulsifier is used asthe comparative agent.

    ______________________________________                                                   Infection of the leaves after spraying with                                   aqueous dispersions or emulsions; . . . % by                       Microcapsule                                                                             weight of active ingredient in the spray liquor                    dispersion 0.1      0.05     0.025 0.012 0.006                                ______________________________________                                        Example 1  0        1        2     3     3                                    Example 3  0        0        1     1-2   3                                    Non-encapsulated                                                              tridemorph 0(2D)    1(1H)    2     3-4   4                                    (comparative                                                                  agent)                                                                        Control    4                                                                  (untreated)                                                                   ______________________________________                                         0 = no infection, graded up to 5 = total infection                            () = leaf damage: 2D = numerous leaf necroses; slight damage                     1H = chlorosis; indication of damage.                                 

EXAMPLE 5

Barley mildew

Using the procedure described in Example 4, barley plants of the "Asse"variety are treated, and dusted with oidiae (spores) of barley mildew(Erysiphe graminis var. hordei).

    ______________________________________                                                     Infection of the leaves after spraying                                        with aqueous dispersions or                                                   emulsions;. . .% by weight of                                    Microcapsule active ingredient in the spray liquor                            dispersion   0.1       0.05     0.025                                                                              0.012                                                                              0.006                               ______________________________________                                        Example 1    0         0        0    0    1                                   Example 2    0         0        0    0    0                                   Non-encapsulated                                                              tridemorph   0         0        1    1    2                                   (comparative agent)                                                                        (2-3AD)   (1-2C)                                                 Control      4                                                                ______________________________________                                         0 = no infection, graded up to 5 = total infection                            () = leaf damage: 2-3AD = numerous necroses; medium leaf damage                  1-2C = some necroses; slight leaf damage.                             

It follows from the experimental results that the fungicides accordingto the invention show, compared to the non-encapsulated product, animproved fungicidal activity in some cases, together with improvedtolerance.

EXAMPLE 6

To prepare very small microcapsules with a diameter of from 0.1 to 0.5μm, 142 parts by weight of tridemorph are dissolved in 130 parts byweight of chloroform, using a method similar to that of Example 1. Thissolution is thoroughly dispersed, at room temperature, in a mixture of66 parts by weight of "Texapon K 12" emulsifier from Dehydag, 400 partsby weight of water, 1.0 part by weight of tributylamine and 0.94 part byweight of p-toluene-sulfonic acid. A solution of 192 parts by weight ofa 40% strength solution of wall material in chloroform/isopropanol, asdescribed in Example 1 of German Laid-Open Application DOS No.2,119,933, and 58 parts by weight of chloroform is then added slowly at40° C., with constant thorough dispersing. After a dispersion time ofone minute, the mean capsule diameter has assumed a value of from 0.1 to0.5 μm.

The emulsion is diluated with 500 parts by weight of water and thechloroform and isopropanol are then distilled off completely.

The capsule wall is hardened by adding 8 parts by weight of 40% strengthformaldehyde solution in the course of 2 hours at 80° C.

The microcapsule dispersion has a solids content of 16.5% by weight anda proportion of tridemorph of 12.5% by weight in the dispersion. Theviscosity, measured by means of a Brookfield viscometer, spindle 1, at100 revolutions per minute, is 16 mPas. It is possible to increase theviscosity, and spray-dry the material, as described in Example 1.Encapsulation is virtually complete; the proportion of tridemorphoutside the microcapsules is less than 0.01% by weight.

The rate of vaporization of the active ingredient from the microcapsulesis less by a factor of 165 than the rate of vaporization of thenon-compounded, non-encapsulated active ingredient.

EXAMPLE 7

The encapsulation by the coacervation process was carried out using theprocess described in U.S. Pat. No. 2,800,457. 20 parts of pigskingelatin are dissolved in 160 parts of water and 2.5 parts ofcarboxymethylcellulose are dissolved in 210 parts of water at 50° C.,the solutions are mixed and the pH is brought to 6.0 by adding 10%strength sodium hydroxide solution. 67.5 parts of tridemorph aredispersed in the mixture of the two colloid solutions, using aUltra-Turrax as the dispersing device, until the particle diameter hasassumed a value of from 2 to 4 μm. The emulsion is diluted with 450parts of water at 50° C., whilst stirring, and the pH is then lowered to4.88 by adding 10% strength acetic acid. After the coacervated capsulehas formed, 3.5 parts of 37% strength formaldehyde solution are addedand the temperature of the dispersion is lowered to 5° C. to gel thewall material. For post-hardening, the pH is brought to 8.17 by adding10% strength sodium hydroxide solution and the mixture is stirred for 12hours at room temperature, i.e. 20° C.

With a tridemorph:wall material ratio of 75:25% by weight, themicro-capsule dispersion obtained has a solids content of 9.5% by weightand a viscosity of 11.3 seconds, measured as the flow time from a DINcup (FB 4).

The dispersion can be concentrated to a solids content of from about 20to 50% by weight, by centrifuging. To prepare a dry powder, either theinitial dispersion or the concentrated dispersion can be spray-dried asdescribed in Example 1.

EXAMPLE 8

Microencapsulation on the interfacial polycondensation principle iscarried out essentially by the process described in U.S. Pat. No.3,429,827.

A solution of 25 parts of terephthalic acid dichloride in 44 parts ofdi-n-butyl phthalate and 44 parts of tridemorph is emulsified in anaqueous solution of 4 parts of polyvinyl alcohol and 0.1 part of sodiumpyrophosphate, using an Ultra-Turrax as the dispersing device.Immediately thereafter, an aqueous solution of 8 parts ofethylenediamine, 0.5 part of 1,6-hexamethylenediamine, 10.3 parts ofdiethylenetriamine, 10 parts of sodium hydroxide solution and 75 partsof water is added, with continuous emulsifying. The mixture is thenstirred for 12 hours in a flask, using a low-speed stirrer.

A microcapsule dispersion with particle diameters of from 3 to 6 μm isobtained. The solids content is about 30% by weight. The viscosity is12.75 seconds, measured as the flow time from a DIN cup (FB 4).

We claim:
 1. A fungicide containing N-tridecyl-2,6-dimethylmorpholine asthe active ingredient, comprising microcapsules which contain the activeingredient and a phthalate plasticizer having a boiling point betweenabout 100° C. and about 250° C. in their core whilst their walls consistof a crosslinked or a formaldehyde hardened or cured non-crosslinkedsynthetic or natural polymer or a mixture of such polymers, said wallsbeing sufficiently impermeable to retard the vaporization of the activeingredient.
 2. A fungicide as claimed in claim 1 wherein said phthalateplasticizer is present in a proportion of from 0% to 50% by weight,based on the weight of said mixture.
 3. A fungicide as claimed in claim2 wherein the weight ratio of said mixture ofN-tridecyl-2,6-dimethylmorpholine and phthalate plasticizer to said wallmaterial is from 3:1 to 15:1.
 4. A fungicide as claimed in claim 1 inthe form of an aqueous microcapsule dispersion.
 5. A fungicide asclaimed in claim 1 in the form of a dry microcapsule powder.